Wing overload failure accident prompts Skymaster AD

October 20, 2010

The FAA has issued an airworthiness directive requiring wing inspections of some aircraft in the Cessna 336 and 337 twin-engine series. The AD, effective Nov. 3, also requires repair of any damage, installing an operational limitation placard in the cockpit, adding limitations to the flight manual supplement, and reporting the results of the inspection to the FAA if damage was found.

The AD covers certain Cessna 336 and 337 airplanes that are, or have ever been, modified by Aviation Enterprises supplemental type certificate (STC) SA02055AT, SA02056AT, SA02307AT, or SA02308AT for wing extensions.

After Nov. 3, inspections must be carried out before further flight, and then every 100 hours time in service, or every 12 calendar months, whichever comes first.

“The FAA reviewed information from the accident investigation, a number of service difficulty reports (SDRs), and data submitted by Aviation Enterprises for demonstrating compliance to the airworthiness standards. Based on the investigation, the FAA determined that Aviation Enterprises may not have adequately substantiated the wing structure for the increased limit and ultimate loads resulting from the wing extension,” said the AD. The FAA also “determined that weight, airspeed, ballast, and ‘G’ limit restrictions need to be placed on these airplanes to allow them to operate within the minimum margins of safety.”

The FAA had issued a special airworthiness information bulletin (SAIB) on March 16, after a modified Cessna 336 crashed in New Jersey following the separation of a six-foot outer wing section. The AD reflects the FAA’s conclusion that the unsafe condition it identified “is likely to exist or develop in other products of the same type design.”

The FAA estimated that 12 U.S.-registered aircraft would be affected by the AD.